Support Dify External Knowledge API

[thiner]

Dify is a powerful LLM app development platform. It contains a built-in RAG system. Dify supports external knowledge base by exposing an API to other RAG systems. The API specification: https://docs.dify.ai/guides/knowledge-base/external-knowledge-api-documentation
If Byaldi can support the API, it will bring Byaldi to a broader visibility of Dify users, and I believe that would attract more attention to Byaldi, and accelerate Byaldi evolution, too.